According to NYCe, the weight different is 3 lbs, not 3 Kg (6.6 lbs) - 11 Kg vs 9.7 Kg.

3 lbs won't make a big difference riding (remember, you're going to be on the bike); it will make a difference when carrying the bike. More expensive components may make the more expensive bike nicer to ride (but for the most part, the cheaper Tern seems reasonable enough).

But when you fold it, you will need a hex wrench to free its handlebar. Unlike the conventional handlebar latch, this one keeps in firmly in place and yields a really solid ride.Most high-end Terns would feature a VRO synthace handlebar, but this impedes folding if you require a compact and fast action on the go. It's a little price to pay for performance, but when you are used to it, its not a hassle.

Think cost estimations of upgrading after purchase. Maybe you need those gears.

Cost was a factor when I bought the Tern C7 but when it was time to upgrade, I would have been better off buying the P9. The C7 provided no means of upgrading unless I was willing to replace the wheelsets, get new cassette/RD and shifters. In the end I sold the bike and bought another. Make no mistake, the C7 is a decent bike and that's about it, decent. So if there's any plans to upgrade in the future, please factor in the cost for this. It'll save you a lot of heartaches, not to mention pocket aches.